1. Field of the Invention
The invention pertains to the field of simulators for sonar systems, and more particularly, for a simulator for a sonar system operating at dockside where a ship is near zero velocity.
2. Description of the Prior Art
A Navigation Sonar System (NSS) is highly complex, requiring large software/firmware programs, extensive hardware, generally contained on a multiplicity of printed circuit boards. In these systems, a Navigation Equipment Program (NEP) in a Memory Processor (MP) computer initiates transmit and receive commands. In a velocity mode, the NSS periodically provides transmit commands to sonar transducers positioned to direct sonar pulses vertically to the ocean bottom. Pulses returned from the ocean bottom are received in each of 16 hydrophones which are arranged on the perimeter of a square. These received signals are processed to obtain digitized signal data in the form of in-phase (I) and quadrature (Q) components which are coupled to the NEP. The I and Q data signals, by a correlation technique, are utilized by the NEP to determine the ship's velocity.
A second mode in the NSS determines the bottom depth below the ship's keel by transmitting a single pulse and noting the return time of the reflected pulse from the bottom. To maintain equipment accuracy, a third mode designated "Ready", utilized when the system is inactive, calibrates the receive channels without transmitting a sonar phase. A NSS Subsystem Program (NSP) within the MP edits the ship's inertial data (ESGN), provides the edited data to the NEP, filters NEP velocity estimates, and interfaces the NSS to the Ship's Navigation System. Numerous other data components are provided to the NSS from the Ship's Navigation System and the Central Navigation Computer. Should any of these systems be operating improperly, erroneous data will be supplied to the NSS and serious navigational errors could result. Testing the system in its operating environment is costly and time consuming. It is therefore desirable to develop an environmental simulator for testing the NSS in controlled simulated operating environments, including dockside.